Ultrastructure of irritant and allergic contact dermatitis

Abstract

Electron microscopy has provided us with a valuable tool to investigate the cellular and subcellular effects of topical exposure to irritants and allergens, complementing histological examination at the light microscope level. Most reported data are based on the use of conventional preparative techniques, but developments such as post-fixation in ruthenium tetroxide to visualize intercellular lipids and the parallel examination of semi-thin and ultra-thin resinembedded samples have enhanced our understanding of the cellular changes that take place. It is important to remember, however, that electron microscopy gives us only a snapshot of a minute fraction of a skin biopsy. Therefore, studies employing small sample numbers, with limited scrutiny of each specimen, should be viewed with a degree of caution. This is particularly true for irritant contact dermatitis investigations, where considerable inter-individual variation in the intensity of the response to chemicals occurs, and where the cellular damage inflicted is rarely uniform across the application site. In the sections which follow, ultrastructural changes seen in skin exposed to irritants and allergens are described.With the exception of the last section, which deals specifically with a recent study of chronic chromate hand dermatitis, the data refer to the effects of acute exposure.